Adjustable Pinhole

ABSTRACT

An adjustable pinhole, in particular for a beam path for illumination and/or detection in a laser-scanning microscope. The pinhole consists of at least two planar basic modules, which have frame-like joints, on which at least one sharp edge is arranged in a displaceable manner in one direction, whereby the basic component advantageously contains at least one integrated, preferably optical or electromagnetic positioning element. A device is provided at the sharp edge, or connected with it, for preferably optical or electromagnetic detection of the position, and is provided, advantageously, with two asymmetric apertures, with mutually opposite orientation, for optical detection of the position, whereby in front of or behind the apertures, a slit is provided, oriented preferably at a right angle to the direction of displacement, and the quantity of light passing through the slit is detected separately for each aperture.

CROSS REFERENCE TO RELATED APPLICATIONS

The present patent application is a nationalization of InternationalApplication No. PCT/EP2004/004498, filed Apr. 28, 2004, which is basedon, and claims priority from, German Application No. DE 103 23 922 A1,filed May 22, 2003, both of which are incorporated herein by referencein their entireties.

FIELD OF THE INVENTION

The present invention relates to adjustable pinholes for use in laserscanning microscopes.

BACKGROUND OF THE INVENTION

A scissors-like shutter mechanism for a pinhole has been described inU.S. Patent Application 2003/0184882 A1, published on Oct. 2, 2003.

In such mechanisms, above all, the accuracy at the sites of the angles,which lie mutually opposite and which must move about an axis ofrotation, poses a serious problem in the fabrication of pinholeapertures with reproducible and light-tight shutting and exact quadraticform.

The problem lies in the fabrication of high-precision pinholes which canshut in a light-tight manner, and whose apertures exhibit a quadraticform from size zero onwards.

SUMMARY OF THE INVENTION

The special advantages of the present invention lie in thequasi-monolithic and very flat design with a “sandwich” style ofconstruction, whereby, according to the invention, the optical positionmeasurement unit can also be integrated directly into it. Regulation ofthe pinhole position can be done with a closed measurement circuitwithout hysteresis effects. The invention can be realized with a numberof materials, among others, with silicon wafer material. Thus, analready miniaturized design can be miniaturized even further. Energyconsumption for the actuation is low. Production costs are very low.

The basic module consists of at least one monolithic planar structure,which comprises at least one sharp edge, built in the interior, and heldby elastic joints, and preferably containing at least two triangles,situated in a fixed spatial relationship with mutually oppositeorientation, which serve the purpose of controlling the position(Optical Position Measurement Unit OPM).

Further, the position control comprises flat structures, preferably ofthe same material as that used in the basic modules, which include smallsources of light (for example LEDs) or receivers with adapteddimensions, and are plugged in the sandwich structure of the basicmodules. Further details about the function of the OPM will be presentedin the following description.

The sharp edges of the basic modules are mutually parallel and can beslanted, so as to achieve better closure.

The mechanical arrangement of the integrated mobile elements, preferablya parallelogram attachment in this case, ensures parallelism of both ofthe edges, which are mutually displaceable. The movement of the edgestakes place by means of miniaturized magnetic actuators, preferably, butnot exclusively, of a moving magnet type, whereby, within an electricalcoil, one or more permanent magnets, or a different type ofelectromagnetic actuator, are arranged in a displaceable manner.

Thereby, it is of advantage, if the magnetic actuators are arranged onthe same planar structure as the edges and move the edges. The couplingof the movable edges with the optical position measuring units enables amanipulation of the edges by means of a closed control circuit. With apinhole according to the invention, at least the followingspecifications can be realized:

apertures with a 3-300 μm diameter;

a drift-free movement range of ±300 μm;

reproducibility of the position and opening of an edge less than 500 nm;

compact build in an area smaller than 50×50 ×20 nm;

accuracy of an edge smaller than 0.8 μm;

a high degree of stiffness of the edges (small axial overlap error);

independence of the wavelength within the range of at least 350-800 nm,as well as in IR and UV range; and

a set-up time less than one second.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described in detail on the basis ofthe schematic diagrams.

FIG. 1 is a perspective view of the basic design of the invention.

FIG. 2 is a perspective view of the drive.

FIG. 3 is a partial perspective/schematic view of the optical measuringsystem.

FIG. 4 is an exploded view of the individual components of the inventivepinhole.

DETAILED DESCRIPTION OF THE INVENTION

In describing preferred embodiments of the present invention illustratedin the drawings, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected, and it is to be understood that eachspecific element includes all technical equivalents that operate in asimilar manner to accomplish a similar purpose.

A planar structure S of the basic component consists of an externalframe R in which narrow elastic frames ST are incorporated, whichexhibits recesses RE at their joints in order to keep the junctionpoints small and elastic.

The frames ST hold two elongated inner base plates G1 and G2, on whichthe two edges Sc1 and Sc2 are fastened with their parallel edges lyingopposite to each other. On the base plates G1 and G2, magnets M of anelectromagnetic actuator Ac are fixed sideways, which project into anelectric coil SP fastened on the frame R.

Through electrical regulation, the magnets move into the coils and causetherewith the movements of the edges Sc1, Sc2 against each other in thedirection of the arrow Ar.

The elastic frames ST move perpendicular to their longitudinal directionand are elastic at their joints RE in that direction, while thearrangement perpendicular to the direction of the movement of the edgesexhibits a high degree of stiffness. With reference to FIG. 3, only thetriangles D1 and D2 for each edge of the position control OPM are shown.

If two planar basic modules are joined as in FIG. 1 with each other insuch a manner that the edges of both the basic modules shut making anangle with each other, preferably 90 degrees, then by making thecorresponding changes in the distance of the sharp edges, a highlyprecise, variable rectangle, preferably a square, can be formed, whichcan serve as the pinhole in a laser scanning microscope.

In FIG. 2, the magnet M and the electrical coil SP of an electromagneticactuator are shown in an enlarged perspective view. In FIG. 3, theoptical measuring system is shown.

Behind the triangles D1, D2 with mutually opposite orientation, whichare arranged in a row perpendicular to the direction of the displacement(arrow), a slit AP, oriented at a right angle to the direction of thedisplacement is arranged (there can also be two slits), which areilluminated by one, or preferably two, LEDs L1, L2, for each of thetriangular aperture.

Due to the movement of the edges, the transmission area of the trianglesD1, D2 changes with respect to the slit or the slits AP. This means achange in the quantity of light, which is registered, separately foreach triangle, by the two detectors DE1, DE2 located on the other side,opposite the source of light.

The difference in the quantity of light forms the control signal whichis proportional to the path of the displacement X, while the sum of thedetector signals remains the same and hence ensures that the signal isindependent, in first approximation, of the fluctuations in the quantityof light.

Through the registration of the control signals in the X and Ydirection, the information about the state of the opening of the pinholeis obtained. The calibration of the adjustment device can be done bymeans of external measurements or directly in a laser scanningmicroscope (LSM).

The position detection element can naturally be also realized by meansof other types of non-optical sensors, such as, a capacitive, aninductive, or an electromagnetic sensor, as long as an electricalfeedback signal is made available by means of the position detectionelement.

In FIG. 4, the individual elements that make up the inventive pinholeare arranged symmetrically about the aperture plate with the slitapertures, and consist of 2 basic modules with the edges for themechanical pinhole aperture, photodetector plate for the detection ofthe quantity of light, and the cover plate for the electronic componentsand for covering against stray light.

All planar elements are positioned and fixed using pins (not shown). Allelements can be realized by means of diverse types of processing methodsusing various materials, in particular, metallic materials, ceramicmaterials, semiconductors and synthetic materials.

It is to be understood that the present invention is not limited to theillustrated embodiments described herein. Modifications and variationsof the above-described embodiments of the present invention arepossible, as appreciated by those skilled in the art in light of theabove teachings. It is therefore to be understood that, within the scopeof the appended claims and their equivalents, the invention may bepracticed otherwise than as specifically described.

1-10. (canceled)
 11. An adjustable pinhole, for a beam path for at leastone of illumination and detection in a laser scanning microscope, thepinhole comprising: at least two planar basic modules, which haveframe-like joints, on which a sharp edge, which is displaceable in atleast one direction, is mounted.
 12. The pinhole according to claim 11,whereby a basic module comprises at least one integrated positioningelement.
 13. The pinhole according to claim 11, whereby a basic modulecomprises two mutually displaceable sharp edges, which cover apreferably parallel interspace.
 14. The pinhole according to claim 11,whereby two basic modules are each provided with two sharp edges and thedirection of the displacement of the basic modules cover an angle ofabout 90 degrees.
 15. The pinhole according to claim 11 whereby at thesharp edge, or connected with it, means are provided for optical orelectromagnetic detection of the position.
 16. The pinhole according toclaim 11, whereby for the optical detection of the position, twoasymmetrical apertures with opposite orientation are provided, which areradiated by at least one source of light, provided with a slit,preferably perpendicular to the direction of the displacement in frontof or behind the apertures and the quantity of light passing through theslit is detected separately for each aperture.
 17. The pinhole accordingto claim 16, wherein the apertures comprise two triangles with mutuallyopposite orientation.
 18. The pinhole according to claim 11, whereby foractuation of the displacement, electromagnetic actuators are provided.19. A device for optical detection of the position and the opening of apinhole with at least two elements with mutually variable positions,which enclose a variable opening between them for light, particularly inthe beam path for illumination and/or detection in a laser scanningmicroscope, the device comprising: two asymmetric apertures withessentially mutually opposite orientation at least one light source forilluminating the two apertures; and a slit in front of or behind the twoapertures, whereby the quantity of light passing through the slit isdetected separately for each of the two apertures.
 20. The deviceaccording to claim 19, whereby the position and the opening of the sharpedges are controlled by means of an integrated optical measuring systemin a closed control circuit.
 21. The pinhole according to claim 12,wherein the integrated positioning element comprises an opticalpositioning element.
 22. The pinhole according to claim 12, wherein theintegrated positioning element comprises a capacitive positioningelement.
 23. The pinhole according to claim 12, wherein the integratedpositioning element comprises an electromagnetic positioning element.